1917 was dominated by two big offensives on the Western Front. The French Nivelle Offensive in April was a disaster that left the French Army in chaos. The Third Battle of Ypres, launched by General Haig in July, saw soldiers fighting in a hellish bog caused by unusually heavy rain.
Meanwhile events away from the battlefield meant big changes for the Western Front. America declared war on Germany in April and by the end of the year thousands of American soldiers had arrived in France. At the end of the year the Russian Revolution resulted in Russia leaving the war. This allowed Germany to move soldiers from the Eastern to the Western Front ready for 1918.